Flap for airfoils



1.941- R. T. YOUNGMAN 2,252,656

FLAP FQR AIRFOILS Filed July 25, 1958 3 Sheets-Sheet l INVENTOR ROBERTTALBOT YOUNGMA ATTORNEYS Aug. 12, 1941. R. T. YQUNGMAN 2,2 2 656 O FLAPFOR AIRFOILS Filed July 25, 1958 5 Sheets-Sheet 2 INVENTOR V ROBERTTALBOT YOUNGMAN MW ATTORNEYS Aug. 12, 1941. R. T. YOUNGMAN FLAP FORAIRFOILS Filed July 25, 1938 3 Sheets-Sheet 3 INVENTOR ROBERT TALBOT.YOUNGMAN Y?) ATTORNEYS Patented Aug. 12, 1941 emomci:

FLAP; FOR. AIRFOILS 'Robert Talbot Youngman, Church Crookha-m, V, iAldershot, England, assignor to The Fairey Aviation Company Limited,Hayes,,Middle s ex,

England Application July 25, 1938, Serial No. 221,227 T In Great BritainAugust 19,1937 a t The high speed of modern aircraft is achieved largelyby increasing the'wing loading of a main airfoil and it is well xknownthat aircraft-having a high wing loading require long takeoff andlandingruns.- w

"It is necessary'in orderto reducethe run required to increase thenormal lift and drag of a main airfoil, and for this purpose trailingedge flaps and the like havebeeniproposed. It is highly desirable,however, that the drag should be increased beyond the value obtainingwhen the flap has been moved to the position giving maximum lift so thatthe angle of glide may be steepened without consequent increaseinthe-speed of the aircraft. 1

' Depression of the trailing edge of a ilap'or winglet (by which ismeantan auxiliary airfoil positioned near the trailing edge of' a mainairfoil, but with its'leading edgesomewhat in rear of said trailingedge) increases the lift of the main airfoil progressively until theflap or winglet is at an angleof approximately 50 to the chord of themain airfoil, at which position the lift has reached a maximum value. Ithas been found, however, that if the trailing edge of the flap orwinglet be still further depressed the lift 1 remains substantiallyconstant, butthe drag increases whilst if, instead of the trailing edge,the leading edge of the flap or winglet be depressed considerably, alarge increase in drag also results.

It is the object of the present invention to provide improvedlmeans,readily operable by the pilot of the aircraft, for increasing the dragupon the airfoil whilst maintaining conditions of maximum lift and alsoto provide high drag without increase in pitching moment.

According to the invention, a flap or winglet for an aircraft isarranged to be lowered bodily below the level of a main airfoil, and, tobe turned about an axis at or near to the centre of pressure to depressor raise the leading edge of the flap until the plane of the latter issubstantially normal to that of the main airfoil.

The invention will now be described by way of example with reference tothe accompanying drawings, of which Figure 1 is a fragmentarydiagrammatic side elevation of a main airfoil and flap assembly inaccordance with one form of the invention, Figure 2 is a fragmentarysectional plan view of the flap and associated operating mechanism to alarger scale, and Figure 3 is a similar view to Figure 1 showing amodified form of the invention.

Referring to Figures 1 and 2, II indicates the 2 Claims. (01. 244 -42)main airfoil and l2 a flap carried by a pair of links l3, I4 in themanner describedin the: specification of my co-pending applicationSerial Number 113,658, but the pivotalconnections'of the links l3, l4and their, lengthsane such that, when the flap 'l2is initsloweredposition, its trailing edge-lies belowand in rear of the trailingedgeuof the mainairfoil IL; The lower ends of the links I3 I4qarepivotally connectedlby a subsidiary link l5 which may normally liewithin the flap l2. The upper end of the forward link I3 is rotatable asone with a worm wheel l6 meshing with a worm I'lfastonia shaft l8. Theshaft I8 may be-rotated from a crank handle 1 l9 inthe cockpit of theaircraft to cause lowering orraising, of the fiaplZ, and the arrangementis such that when the flap I2 is lowered to thepositioncof maximum lift,the forward (or shorter)?" link I3 and the subsidiary link [5 lie in astraight line, as indicated diagrammatically at |3','l'5 ".1 1 1 r '-Inthis way a triangulated structure is obtained between the shorter linkl3 and the subsidiary link l5 (forming together one side), the longerlink l4, and that portion of the main airfoil II; or apart mountedthereon, between the upper ends'of the shorter and longer links l3, [4.The flap I2 is thus firmly held in position.

The flap I2 is rotatable about the lower pivot point of the rear (orlonger) link I4 and the forward partcof the flap I2 is detachablyconnectedwith the lower pivot of the front (or shorter) link l3 as willbe more fully described hereinafter.

Coaxially with the lower pivotal point of the rear (or longer) link Hi,there is mounted, a sprocket wheel '20 connected by a-chain 2| with asecond sprocket wheel 22 freely rotatable about the upper pivotal axisof said link 14. A third sprocket wheel, coaxial with and fixedrelatively to the sprocket wheel 22, is connected by a chain 23 with afourth sprocket'wheel 24 freely rotatable about theupper pivotal axis ofthe forward (or shorter) link [3. Said fourth sprocket is rotatableas'one with a fifth sprocket which is connected to a sixth sprocket 25movable as one withan operating lever 26 (for the sake of clearnessshownin elevation and not in plan in Figure 2) in thepilots cockpit.

The sprocket wheel 20 is freely mounted relati-velyto the'fiap l2-butmay be positively connected therewith through a clutch device which isinterconnected with a similar clutch mechanism for detachably connectingthe flap l2 with the lower pivot of the forward link [3.

of this bell crank lever is pivoted to a rod 32 and to the other end ofsaid rod 32 there is pivoted a plunger 33 which can be moved, when theflap l2 isin the stowed position, through an aperture 34 formed in thebracket 21 into a recess 35 formed in the face of the sprocket wheel 20.The arm 3| of the bell crank lever 30, 3| is connected by a link 36 withone arm 31 of a further bell crank lever 31, 38, pivoted on a bracket 39carried by the forward part of the flap I2. The arm 38 of this bellcrank lever is pivoted to a rod 40 connected with a plunger 4| which canbe moved, when the flap I2 is in the stowed position, through anaperture 42 formed in the bracket 39 into a recess 43 formed in thepivot 44 of the links I3 and I5.

A Bowden cable 45 is connected between one end of the link 36 and asubsidiary control member 46 mounted on the operating lever 26.

The arrangement-is such that normally the plunger 4| extends through theaperture 42 and into the recess 43 so that the leading edge of the flapI2 is positively connected with the pivot of the links I3 and I5, whilstthe plunger 33 is withdrawn from the recess 35 so that the flap I2 isfree to rotate about the pivotal axis of the links I4 and I5 as it islowered.

In use, the flap I2 is lowered by rotating the crank handle I9 and,owing to the relative lengths of the links I3 and I4 the bodily loweringof the flap I2 is accompanied by a turning movement about the pivotalaxis of the links I4 and I5. When the flap I2 has been fully lowered thepilot may grasp the lever 26 and the control member 46 to free the flapI2 from the pivot of the links I3 and I5 and, simultaneously, to connectthe flap I2 with the sprocket wheel 20. By rocking the lever 26 the flapI2 may now be turned, about the pivotal axis of the links I4 and I5, todepress or raise its leading edge until its plane is substantiallynormal to that of the main airfoil I I.

In a modified form of the invention, and as shown in Figure 3, the flap4! is carried, on the one hand, by a two part link 48, 49, the part 48being pivoted to the main airfoil 58 and the part 49 being pivoted tothe flap 41 at or near its centre of pressure, and, on the other hand bya link 5| pivoted, at one end, to the flap coaxially with the part 49and, at the other end, to a part carried by the main airfoil 50. Thatend of the part 48 of the two part link which is pivoted to the mainairfoil 58 carries a worm wheel 52 meshing with a worm 53 which may berotated through a shaft 54 from means, such as a crank handle 54, in thecockpit of the aircraft.

In rear of the pivotal connection of the link 5| and the part 49, thereis pivoted one end of a link 55, the other end of which is pivoted toone arm 56 of a bell crank lever 56, 51 mounted coaxially with the upperend of the link 5|. The arm 51 of the bell crank lever is connected by alink 58 with an arm. 59 rotatable as one with a worm wheel 68 meshingwith a worm 6| which may be rotated through a shaft 62 by subsidiarymeans, such as a crank handle 62', in the cockpit of the aircraft.

If desired, the two part link 48, 49 may be replaced by an hydraulicjack one part of which is pivoted to the airfoil 58 and the other partof which is pivoted to the flap 41.

In use, the flap 41 is first lowered bodily by operation of the worm 53and is then turned about its axis by operation of the worm 6| so thatits leading edge is raised or lowered as may be desired. It will beappreciated that by suitable operation of the worm 5| the flap 41 may bepositioned to suit the various evolutions of the aircraft such as takeoff, landing, and divebombing.

In particular, the invention enables the leading edge of the flap to beraised or depressed even until the general plane of the flap is normalto that of the airfoil and according to the degree of movementremarkable results are obtainable in the control of aircraft havingflaps arranged in accordance with the invention.

It is to be understood that a plurality of mechanisms as described abovemay be provided for each flap or in some cases a plurality of the firstmentioned and two-part links may be provided in conjunction with asingle mechanism for turning a flap about its axis.

In dive bombing, it is a great advantage to in-. crease the drag withoutincrease in lift or pitching moment, and it has been found thatdepression of the nose of the flap or winglet to give a negativeincidence relative to the main wing, increases the drag without such alarge increase in lift as when the trailing edge is-depressed, and alsothe pitching moment of the combined wing and flap is considerably less.

The term flap used in this specification is intended to include awinglet of a main airfoil.

I claim:

1. In an airplane wing, a .fiap, and means mounting said fiap formovement between an upper, retracted position and lower, extendedpositions, comprising first pivot means on said flap, second pivot meanson said flap to the rear of said first pivot means, a crank arm, axlemeans mounting said crank arm on said wing for rotation about a fixedaxis to the rear of said pivot means when said flap is retracted, a linkhaving one end pivoted on said first pivot means and the other endpivoted to said axle means, a second link having one end pivoted to saidsecond pivot means and its other end pivoted to the free end of saidcrank arm, extensible means mounted on said wing and connected to saidfirst pivot means to rock the same about said axle means whereby toswing said flap between retracted and extended positions, and drivingmeans operable independently of said extensible means for swinging saidcrank arm about said axle means whereby to rotate said flap about saidfirst pivot means. 2. The combination claimed in claim 1, saidextensible means comprising a shaft rotatably mounted in said wing, asecond crank arm on said shaft, a third link having one end pivoted tothe free end of said crank arm and the other end pivoted to said firstpivot means, and oneway drive means connected to said second crank armfor rotating the same about said shaft.

ROBERT TALBOT YOUNGMAN.

